Description

This manual page describes the DbException class and how it is used
by the various Db* classes.

Most methods in the Db classes return an int but also throw an exception.
This allows for two different error behaviors, that are known as
error models.
By default, the error model is configured to throw an exception whenever
a serious error occurs.
This generally allows for cleaner logic for transaction processing,
as a try block can surround a single transaction.
Alternatively, the error model can be set to not throw exceptions,
and instead request the individual function to return an error code.
The error model can be changed using the DbEnv::set_error_model
method.

A DbException object contains an informational string and an errno.
The errno can be obtained by using DbException::get_errno.
The informational string can be obtained by using DbException::what.

We expect in the future that this class will inherit from the standard
class exception, but certain language implementation bugs currently
prevent this on some platforms.

Some methods may return non-zero values without issuing an exception.
This occurs in situations that are not normally considered an error, but
when some informational status is returned. For example, Db::get
returns DB_NOTFOUND when a requested key does not appear in the database.